The diamondback moth (DBM) (Plutella xylostella) is the world’s worst insect pest of brassica crops (cabbages, canola, broccoli, cauliflower, kale, etc.) – costing farmers $4-5 billion annually worldwide. The moths are small, about the length of two grains of rice, but females can lay upwards of 150 eggs during their lifetime and a generation can be produced in as little as two weeks. This invasive pest probably originated in Europe, but is now found throughout the world, including New York State and other states that farm brassica vegetables.

Where and when is this research taking place?

Following successful completion of laboratory and greenhouse studies in the UK and US at Cornell, contained field cage trials are planned for the summer 2015. The field trials will take place on a research farm at Cornell’s New York State Agricultural Experiment Station in Geneva, NY during the growing season of 2015. These studies will inform the next steps for further field evaluation of this moth.

What is this research?

The Diamondback Moth Project is a scientific evaluation of a way to manage local pest populations of DBM using a control method developed by Oxitec (http://www.oxitec.com/). The control method involves genetically engineering a strain of DBM to be effectively ´´sterile´´. In greenhouse studies conducted at Cornell and the UK, the release of genetically engineered (GE) male Oxitec DBM was able to control the target pest DBM populations. The Diamondback Moth Project is now taking the next step to evaluate the effectiveness of this technique for the reduction of pest DBM in controlled field trials.

The first trial will take place in contained field cages, each about 24 (length) x 12 (width) x 7 (height) feet. Cabbages and GE and non-GE DBM will be introduced into the cages. These cage studies have four objectives: a) assess mating competitiveness of male GE moths; b) assess longevity of male GE moths; c) assess the reproductive rate of pest moths; and d) test the suppressive effect of male GE moths on the pest DBM. The results of the caged studies will inform us on how the GE moths behave in outdoor conditions, and how they might be applied in future crop protection programs.

How does this pest control method work?

This approach for insect control is based on the Sterile Insect Technique (SIT), which has been used worldwide for more than 50 years to control several important insect pests. However, with traditional SIT, male insects are sterilized with radiation and then released to mate with local female pest insects of the same species. Because the males have been sterilized, there are no offspring from the mating and this reduces the pest population over time with multiple releases. A challenge of SIT is that the radiation can affect many different genes and reduce the fitness of the male insects so they are less competitive for mating with the pest population, so Oxitec scientists developed a way to produce the same sterility effect using targeted genetic control instead of radiation. How it works is that the DBM have two added genes: a ‘self-limiting’ gene that acts as the pest control to prevent offspring from surviving to adulthood, and a color marker to track and trace the insects in the environment and to distinguish Oxitec insects from the local pest ones.

Why is Cornell doing this research?

Improved methods for managing DBM are needed in New York and worldwide, and this control method, like all applications of science, requires a critical evaluation. A Cornell scientist, Professor Anthony Shelton (http://shelton.entomology.cornell.edu/), is a world expert on DBM and will be conducting the research in association with scientists from Oxitec, a spinout company from Oxford University, who developed the moth strain.

Who benefits from this research?

New York growers, as well as growers throughout the world, typically spray their crops with insecticides to reduce injury caused by DBM larvae. This has led to the insect developing resistance to most insecticides and increased levels of crop damage, as well as increased concerns about worker safety, pesticide residues on crops, and potential hazards to the environment. Using Oxitec DBM does not have these drawbacks because they control just this invasive pest. Such species-specific control and a reduced reliance on insecticides can help protect other beneficial organisms such as pollinators, predators and parasitoids.

Will this research negatively impact the environment or other agriculture?

No, for the following reasons:

The proteins from the color marker and self-limiting gene are non-toxic and non-allergenic, so if a human, bird or other organism ate an Oxitec DBM the effect would be the same as eating a wild one.

The Oxitec DBM only mates with its own species so the genes do not spread. This species-specific control is different from the use of insecticides in which other species vulnerable to insecticides, including beneficial organisms, can be affected.

Only male DBM adults are released and they mate with local females. The released moths and their offspring die, and the female offspring die before reaching adulthood because of the self-limiting gene. This means that the insects and their genes do not persist in the environment.

DBM only feeds on plants in the cabbage family so they will not affect other crops including corn, soybeans, apples, and other non-brassica crops.

This research project with GE DBM will not affect certification of other types of agricultural production including organic, conventional or biotechnology.

The moths will not survive into the next season because:

They cannot survive the winter temperatures of upstate New York.

The adult moths live for just a few weeks.

Are special permits required for this work?

Yes. On August 28, 2014 the Federal Register published a notice (http://www.aphis.usda.gov/brs/fedregister/BRS_20140828b.pdf) advising the public that APHIS (Animal and Plant Health Inspection Service) was making available their environmental assessment for the proposed Oxitec DBM release and would consider all comments. The APHIS comment period ended with a total of 283 comments. APHIS considered all comments and then approved a permit on November 10th, 2014 for field trial releases of the Oxitec DBM. The contained field cage study is the next step following successfully completed lab and greenhouse studies.